More subscribers, networks with better coverage and devices that can be used in more countries are converging to make LTE roaming a more viable proposition, with some operators already offering such services on a limited scale and more on the way.

"We were at Mobile World Congress last month and members of our executive team and our global roaming team were there actively seeking roaming partners, so that we can offer our customers 4G LTE when they are traveling and also offer customers of other providers overseas the option to roam on our network," said Tom Pica, executive director of corporate communications at Verizon Wireless.

The first fruits of those deliberations will come in early 2014, when Verizon will start offering its subscribers "LTE roaming in several countries, including Canada," according to Pica, who is convinced the operator's subscribers want that service.

Across the Atlantic, TeliaSonera became the first to offer LTE roaming in Europe last month, allowing its users in Denmark to access LTE when visiting Sweden. The next step will be to add more countries where it has its own networks, but roaming deals with other operators are also being worked on.

"I wouldn't be surprised if we are ready to roam with an external operator this year," said Tommy Ljunggren, vice president of System Development at TeliaSonera's Mobility Services.

Both Telstra, which is based in Australia, and TeliaSonera are charging the same for LTE and 3G roaming. The Australian operator announced a deal with its subsidiary CSL in Hong Kong earlier this year, and is working on similar agreements with operators in other countries, it said.

The spectrum bands supported by smartphones, tablets and USB modems determine the countries in which users can roam, assuming agreements between operators are in place. Smartphones like the Samsung Galaxy S4 and Sony Xperia Z are leading the way by implementing up to six LTE bands.

The most commonly used frequencies today are 1800MHz and 2600MHz, which provide coverage in about 80 percent of the countries where commercial LTE services are available, according to Alan Hadden, president at industry organization GSA (Global mobile Suppliers Association). That includes Europe, parts of Africa, Asia and South America.

Those two bands will be supported by the European LTE version of the Galaxy S4, which can also access LTE networks on the 800MHz, 850MHz, 900MHz and 2100MHz bands, Vodafone, Orange and TeliaSonera confirmed. The Xperia Z has the same band configuration, according to Sony Mobile's website. The addition of those four bands provides better coverage in mainly Europe and Asia, including Japan and South Korea. The 800MHz band will play an important role in Europe, because of the good coverage characteristics it offers, Ljunggren said.

That still leaves the U.S., which is high on any operator's list of countries for LTE roaming, but offering the service isn't so straightforward. That's because U.S. operators such as Verizon and AT&T Mobility use different parts of the 700MHz band, which offers superior coverage and is therefore the best alternative when roaming. The short-term answer is for the European and Asian operators to choose which U.S. operator to align with, Hadden and Ljunggren agreed.

"That is a choice an operator can make, but more importantly it is a choice that device manufacturers will make," Ljunggren said, and added that phones will still have roaming service using 3G.

In addition to 700MHz, devices that have implemented AWS spectrum (1700MHz and 2100MHz) will also be able to access LTE in the U.S. Where U.S. consumers will have roaming service, other than in Canada, remains to be seen. Verizon will introduce products when the time is right, according to Pica, who wasn't willing to elaborate about what bands its version of the Galaxy S4 will handle.

Enabling data roaming on LTE, which includes implementing signaling protocol Diameter, hasn't been easy, according to Martin Guilfoyle, vice president of new products and R&D at Syniverse Technologies.

Operators that want to offer LTE roaming can either connect directly with each other or turn to an intermediary like Syniverse and connect to multiple other operators via their platform. Guilfoyle has been working on this for close to three years, and last year really culminated in a trial and proof-of-concept that has now been turned into a production environment.

"It hasn't been a trivial task; it took a lot of planning," Guilfoyle said.

The current situation reminds him of when GSM was rolled out in the beginning of the '90s.

"There were pockets of roaming, and then all of a sudden everybody and their cousin wanted to have a roaming agreement with everybody," Guilfoyle said.

For operators, offering LTE roaming comes with both potential risks and rewards. That services have been slow to materialize has more to do with commercial considerations rather than network complexities, according to Mark Newman, chief research officer at Informa Telecoms & Media.

"Operators are concerned that if they don't get the retail pricing structure right, LTE roaming could end up cannibalizing their revenue from voice and SMS roaming," Newman said.

One threat is from users switching to services like Skype, WhatsApp and iMessage, which are already putting pressure on operator revenue, and will work even better on LTE with its superior performance.

"It is up to us to offer services that are so good users won't want to do that," Ljunggren said.

Operators also want to get their hands on data revenue that is lost when subscribers travel abroad and connect using local Wi-Fi networks.

"Today business users spend a lot of money on Wi-Fi connectivity in hotels and at airports when roaming abroad, and operators should really [be able] to capture that revenue," Newman said.

Copyright 2017 IDG Communications. ABN 14 001 592 650. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of IDG Communications is prohibited.